The invention relates in general to tube-launched projectiles and in particular to obturators for such projectiles.
Obturators are used on tube-launched projectiles to create a gas seal. The propellant gas behind the obturator propels the projectile out of the launching tube. Slip obturators decouple the rifling effects of a rifled launch tube from the projectile. Slip obturators enable fin-stabilized munitions to be launched from rifled barrels with a minimum of barrel-induced spin or from smooth barrels with no barrel-induced spin.
Some projectiles and their obturators are designed to be launched from rifled tubes while other projectiles and their obturators are designed to be launched from smooth bore tubes. For various reasons, a smooth-bore projectile may be launched from a rifled tube. For example, a smooth-bore mortar round may be launched from a rifled mortar tube. When this occurs, an increased amount of propellant gas blows by the obturator. The increased blow-by gas decreases the energy available to propel the projectile. The increased blow-by can also harm the projectile and tube in several ways. For example, the increased blow-by gas may cause the projectile to ballot (oscillate side to side) in the launch tube. The increased blow-by gas may also overheat portions of the projectile located forward of the obturator or erode the rifling inside the launch tube.
Examples of known obturators are disclosed in U.S. Pat. No. 6,295,934 issued on Oct. 2, 2001; U.S. Pat. No. 6,981,450 issued on Jan. 3, 2006; U.S. Pat. No. 5,164,540 issued on Nov. 17, 1992; U.S. Pat. No. 3,760,636 issued on Sep. 25, 1973; U.S. Pat. No. 3,910,194 issued on Apr. 25, 1973; U.S. Pat. No. 6,419,235 issued on Jul. 16, 2002; WIPO publication WO2010025891 published on Mar. 11, 2010; U.S. Pat. No. 2,846,281 (piston ring) issued on Aug. 5, 1958; and European Patent Office publication EP0046888 published on Mar. 10, 1982.
A need exists for an improved obturator for projectiles that are muzzle-loaded and launched from rifled tubes.